forming a sort of spurious margin: their apex sometimes
regularly dimpled, with a central pore; but mostly irregular,
both dimple and pore, and often the whole shell, becoming
rugged and uneven, and the tubercle, in some cases,
assuming the appearance of an imperfect patellula: nucleus
obscure, sometimes white, sometimes almost black ; its base
not inclosed by the shell.
T. he Lichen before us differs from V. rupestris of Schrader
by its limited and even crust, and its more prominent and
larger tubercles. It is also of a much neater and more
regular appearance. In V. immersa of Hoffmann (PL L ichen.
t.1 2 . f.2—‘4), which should probably be separated from
V. rupestris, the tubercles are still smaller. In both these
Lichens the tubercles possess, more remarkably than in
V. concinna, the property of excavating and forming hollows
in the stone ; and, in both, the nucleus is either subtended
by the shell, or is inclosed in a black inner perithecium.
In the specimen figured in Engl.Bot. 1.1711, as Lichen
Schraderi, V. rupestris and V. immersa appear to have grown
intermixed, as they frequently do on chalk. V. Schraderi
of Acharius probably includes V. rupestris and V. immersa,
and,judging from the specimen communicated by that author
to the Linnean Society, some other species also. In his
Synopsis Lichenum Hoffmann’s figures are referred to, with
doubt, under Lecidea immersa. W. B.
V E R R U C A R I A laevata.
Greyish Water Verrucaria.
CRYPTOGAMIA Lichenes.
G e n . C h a r . Tubercles of a different substance from
the thallus, simple, convex, not expanding but
furnished with a central pore, and inclosing a
somewhat gelatinous nucleus.
S p e c . C h a r . Crust thin, tartareous, cracked, smooth,
dirty white or brownish grey. Tubercles small,
partially emerging, somewhat conical, black.
S y n . Verrucaria lsevata. Ach. Lich. Univ. 284.
Syn. 94.
K jOCKY beds of streams in mountainous districts produce
this Lichen. Our specimens were sent from the North
of England by the Rev. J. Harriman. Mr. Robertson has
favoured us with the same from Teesdale, and the late Sir
T. Gage found it at Killarney.
The crust, often scarcely more than a film, is sometimes
as thick as the shell of a hen’s egg, and then it is white
within, except a thin layer of green near the surface : externally
it is more or less brown in different specimens, not
greenish, as Acharius describes it, unless the surface has
been abraded, nor does its hue change upon the application
of moisture; yet an external tinge of green may possibly
exist in the living plant *. The minute cracks look as if
caused by the shrinking of the originally continuous crust.
They vary much in abundance: in the thicker specimens
they usually divide the whole surface into imperfect, small,
angular areolae. The tubercles are mere specks to the
naked eye, numerous, but rarely crowded ; their base sunk
in the crust, which often rises about them, and obscures, as
* In a Specimen sent by Acharius to the Linnean Society, the crust has
somewhat of a carneous hue, and the tubercles are rather larger than in
ours; yet we believe that specimen to be of the same species.